JP2020111714A - Block isocyanate - Google Patents

Abstract

To provide block isocyanate capable of imparting excellent mechanical characteristic, solvent resistance and weather resistance to a coating film, and also imparting expansion resistance under a high humidity condition, while securing excellent water dispersibility.SOLUTION: An isocyanate group of polyisocyanate containing a reaction product of an isocyanurate derivative of xylylene diisocyanate and a polyoxyethylene compound, which is a reaction product in which the content of an ethylene oxide group is 15 mass% or more and 30 mass% or less, is blocked with a blocking agent.SELECTED DRAWING: None

Description

The present invention relates to blocked isocyanates.

As a polyisocyanate component used for polyurethane paint, a blocked isocyanate having an excellent pot life is known.

For example, a water-dispersible blocked polyisocyanate obtained by reacting a hexamethylene diisocyanate trimer with a polyoxyalkyleneamine and then reacting a residual isocyanate group with dimethylpyrazole has been proposed (for example, patents Reference 1 (Example 1).).

Japanese Patent Publication No. 11-512772

However, the polyurethane paint is required to have characteristics suitable for various usage environments. For example, when the polyurethane paint is used under high humidity conditions, the polyurethane paint is required to have swelling resistance. However, it is difficult for the water-dispersible blocked polyisocyanate described in Patent Document 1 to impart swelling resistance to a polyurethane coating under high humidity conditions.

The present invention provides a blocked isocyanate capable of imparting swelling resistance under high humidity conditions to a polyurethane resin while ensuring excellent water dispersibility.

The present invention [1] is a blocked isocyanate in which an isocyanate group of polyisocyanate is blocked by a blocking agent, wherein the polyisocyanate contains a reaction product of an isocyanurate derivative of xylylene diisocyanate and a polyoxyethylene compound. The reaction product contains a blocked isocyanate having an ethylene oxide group content of 15% by mass or more and 30% by mass or less.

The present invention [2] includes the blocked isocyanate according to the above [1], wherein the isocyanurate derivative of xylylene diisocyanate is modified with an alcohol.

The present invention [3] includes the blocked isocyanate according to the above [2], wherein the modified amount of the alcohols in the isocyanurate derivative of xylylene diisocyanate is 0.1% by mass or more and 8.5% by mass or less. ..

In the present invention [4], the alcohol includes the blocked isocyanate according to the above [2] or [3], which contains a divalent aliphatic alcohol.

In the present invention [5], the blocking agent contains the blocked isocyanate described in any one of the above [1] to [4], which contains a pyrazole compound and/or an oxime compound.

The blocked isocyanate of the present invention is a blocked isocyanate in which polyisocyanate is blocked by a blocking agent, and the polyisocyanate includes a reaction product of an isocyanurate derivative of xylylene diisocyanate and a polyoxyethylene compound, and a reaction product The content of ethylene oxide group in is within the above range.

Therefore, while ensuring excellent water dispersibility, the polyurethane resin can be provided with expansion resistance under high humidity conditions.

The blocked isocyanate of the present invention is a water-dispersible block isocyanate, and is used by being dispersed in water, for example. In the blocked isocyanate, the isocyanate group of polyisocyanate is blocked by the blocking agent. That is, the blocked isocyanate contains the reaction product of the polyisocyanate and the blocking agent, and preferably consists of the reaction product of the polyisocyanate and the blocking agent.

(1) Polyisocyanate Hereinafter, first, the polyisocyanate before being blocked by the blocking agent will be described.

The polyisocyanate includes a reaction product of an isocyanurate derivative of xylylene diisocyanate and a polyoxyethylene compound (hereinafter referred to as a hydrophilic isocyanurate derivative), and is preferably a hydrophilic isocyanurate derivative.

(1-1) Isocyanurate Derivative of Xylylene Diisocyanate The isocyanurate derivative of xylylene diisocyanate mainly contains isocyanurate of xylylene diisocyanate. Further, the isocyanurate derivative of xylylene diisocyanate, in the isocyanurate conversion of xylylene diisocyanate described below, iminooxadiazinedione of xylylene diisocyanate which is inevitably by-produced, and the inclusion of unreacted xylylene diisocyanate is allowed. To do.

That is, the isocyanurate derivative of xylylene diisocyanate is, for example, 92% by mass or more of isocyanurate of xylylene diisocyanate, 6% by mass or less of iminooxadiazinedione, and 2% by mass or less of unreacted xylylene diisocyanate. And preferably consist of them.

Xylylene diisocyanate includes 1,2-xylylene diisocyanate (o-XDI), 1,3-xylylene diisocyanate (m-XDI), and 1,4-xylylene diisocyanate (p-XDI) as structural isomers. .. The structural isomers of xylylene diisocyanate may be used alone or in combination of two or more kinds.

The xylylene diisocyanate is preferably 1,3-xylylene diisocyanate. That is, the xylylene diisocyanate preferably contains 1,3-xylylene diisocyanate, and more preferably 1,3-xylylene diisocyanate.

Next, a method for preparing an isocyanurate derivative of xylylene diisocyanate, specifically, a method for preparing an isocyanurate derivative of xylylene diisocyanate that has not been modified with alcohols (described later) will be described.

To prepare an isocyanurate derivative of xylylene diisocyanate, xylylene diisocyanate is subjected to an isocyanurate-forming reaction in the presence of an isocyanurate-forming catalyst.

The isocyanurate-forming catalyst is not particularly limited as long as it is a catalyst that activates isocyanurate-forming. Examples of the isocyanurate-forming catalyst include triethylamine, tributylamine, triethylenediamine, secondary amine copolymers (for example, secondary amines such as dialkylamines, and monomers copolymerizable with secondary amines (for example, phenol). , Polycondensates of formaldehyde, etc.) such as tertiary amines, for example, Mannich bases such as 2-dimethylaminomethylphenol, 2,4,6-tris(dimethylaminomethyl)phenol, for example, tetramethylammonium, tetraethylammonium , Tetrabutylammonium, trimethylbenzylammonium, tributylbenzylammonium and other tetraalkylammonium hydroxides and weak organic acid salts thereof, such as trimethylhydroxypropylammonium (also known as N-(2-hydroxypropyl)-N,N,N- Trimethylammonium), trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium, and other trialkylhydroxyalkylammonium hydroxides and their weak organic acids, such as acetic acid, caproic acid, octylic acid, myristic acid, and naphthenic acid. Metal salts of alkylcarboxylic acids (for example, alkali metal salts, magnesium salts, tin salts, zinc salts, lead salts, etc.), for example, metal chelate compounds of β-diketones such as aluminum acetylacetone, lithium acetylacetone, etc. Friedel-Crafts catalysts such as aluminum and boron trifluoride, for example, organometallic compounds such as titanium tetrabutyrate and tributyl antimony oxide, for example, aminosilyl group-containing compounds such as hexamethylsilazane, tetrabutylphosphonium hydrogen difluoride And halogen-substituted organic phosphorus compounds such as The isocyanurate-forming catalyst can be used alone or in combination of two or more kinds.

Among such isocyanurate-forming catalysts, preferably tetraalkylammonium hydroxide and trialkylhydroxyalkylammonium hydroxide are mentioned, more preferably tetraalkylammonium hydroxide is mentioned, and particularly preferably. And tetrabutylammonium hydroxide.

The mixing ratio of the isocyanurate-forming catalyst (converted to 100% by mass of the active ingredient) is, for example, 0.001 parts by mass or more, preferably 0.008 parts by mass or more, and more preferably 100 parts by mass of xylylene diisocyanate. It is 0.015 parts by mass or more, for example, 0.1 parts by mass or less, preferably 0.026 parts by mass or less, and more preferably 0.022 parts by mass or less.

The entire amount of the isocyanurate-forming catalyst may be added at the charging stage (initial stage) of the isocyanurate-forming reaction, or may be added plural times during the isocyanurate-forming reaction. The above-mentioned blending ratio is the blending ratio of the isocyanurate-forming catalyst to be blended before the initiation of the isocyanurate-forming reaction (initial) (feeding ratio) and the blending ratio of the isocyanurate-forming catalyst to be added during the isocyanurate-forming reaction (additional ratio). Is the total compounding ratio.

Such an isocyanurate-forming reaction is carried out, for example, in an inert gas (for example, nitrogen gas, argon gas, etc.) atmosphere.

The reaction temperature of the isocyanurate-forming reaction is, for example, 20° C. or higher, preferably 40° C. or higher, more preferably 60° C. or higher, eg 90° C. or lower, preferably 80° C. or lower. The reaction pressure is, for example, atmospheric pressure. The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, more preferably 2 hours or more, for example, 12 hours or less, preferably 10 hours or less, more preferably 8 hours or less.

In such an isocyanurate-forming reaction, a cocatalyst and a stabilizer can be added.

Examples of the cocatalyst include organic phosphite ester, and more specifically, aliphatic organic phosphite ester, aromatic organic phosphite ester, and the like. The co-catalyst can be used alone or in combination of two or more kinds.

Examples of the aliphatic organic phosphite include triethylphosphite, tributylphosphite, tris(2-ethylhexyl)phosphite, tridecylphosphite, trilaurylphosphite, tris(tridecyl)phosphite, tristearylphosphite, and the like. Derived from aliphatic polyhydric alcohols such as distearyl pentaerythrityl diphosphite, di dodecyl pentaerythritol diphosphite, di tridecyl pentaerythritol diphosphite, and tripentaerythritol triphosphite. Examples thereof include a di-, tri- or tetra-phosphite, an alicyclic polyphosphite such as hydrogenated bisphenol A phosphite polymer (molecular weight 2400 to 3000), and tris(2,3-dichloropropyl)phosphite. The aliphatic organic phosphite ester can be used alone or in combination of two or more kinds.

Among the aliphatic organic phosphites, alkyl monophosphite is preferable, and tridecyl phosphite is more preferable.

Examples of the aromatic organic phosphite include triphenylphosphite, tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, diphenyldecylphosphite, diphenyl(tridecyl)phosphite. From aryl monophosphites such as phyto, for example, aromatic polyhydric alcohols such as dinonylphenyl pentaerythritol diphosphite, tetraphenyl tetra tridecyl pentaerythrityl tetraphosphite, and tetraphenyl dipropylene glycol diphosphite. Derived di-, tri- or tetra-phosphite, and further, for example, dialkyl bisphenol A diphosphite having 1 to 20 carbon atoms, 4,4'-butylidene-bis(3-methyl-6-t-butylphenyl) And diphosphites derived from bisphenol compounds such as di-tridecyl)phosphite. The aromatic organic phosphite can be used alone or in combination of two or more kinds.

Among the aromatic organic phosphites, di-, tri- or tetra-phosphite derived from aromatic polyhydric alcohol is preferable, and tetraphenyl-dipropylene glycol-diphosphite is more preferable.

The mixing ratio of the co-catalyst is, for example, 0.01 parts by mass or more, preferably 0.03 parts by mass or more, for example, 0.1 parts by mass or less, and preferably 0.1 part by mass with respect to 100 parts by mass of xylylene diisocyanate. It is not more than 07 parts by mass.

As the stabilizer, for example, a hindered phenol-based antioxidant, more specifically, 2,6-di(tert-butyl)-4-methylphenol (also known as dibutylhydroxytoluene, hereinafter sometimes abbreviated as BHT) Irganox 1010, irganox 1076, irganox 1135, irganox 245 (all manufactured by Ciba Japan Co., Ltd., trade name) and the like. The stabilizers can be used alone or in combination of two or more kinds.

The mixing ratio of the stabilizer is, for example, 0.01 parts by mass or more, preferably 0.02 parts by mass or more, for example, 0.05 parts by mass or less, and preferably 0.1 part by mass with respect to 100 parts by mass of xylylene diisocyanate. It is not more than 03 parts by mass.

Further, in the isocyanurate-forming reaction, known additives may be added at an appropriate ratio and at any timing, if necessary.

Known additives include, for example, organic solvents (described later), catalyst deactivators (eg, phosphoric acid, monochloroacetic acid, dodecylbenzenesulfonic acid, paratoluenesulfonic acid, benzoyl chloride, etc.).

As a result, the xylylene diisocyanate is converted to isocyanurate to produce isocyanurate of xylylene diisocyanate.

The conversion rate of the isocyanate group in such an isocyanurate conversion reaction (isocyanurate conversion rate) is, for example, 10% by mass or more, preferably 15% by mass or more, more preferably 25% by mass or more, for example, 40% by mass. Hereafter, it is preferably 33 mass% or less. The conversion rate of the isocyanate group can be measured according to the method described in Examples below (the same applies hereinafter).

As described above, a reaction liquid (reaction mixture) containing an isocyanurate derivative of xylylene diisocyanate is prepared.

The concentration of free isocyanate groups (isocyanate group concentration) in the reaction liquid of such isocyanurate-forming reaction is, for example, 10% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, for example, It is 50 mass% or less, preferably 40 mass% or less. The isocyanate group concentration can be measured according to the method described in Examples described later (the same applies hereinafter).

The reaction liquid contains unreacted xylylene diisocyanate in addition to isocyanurate of xylylene diisocyanate. Further, the reaction liquid may contain the above-mentioned known additives and the like.

Therefore, the reaction liquid of the isocyanurate-forming reaction is preferably purified by a known purification method. Examples of the purification method include thin film distillation (Smith distillation) and extraction, and preferably thin film distillation.

When the reaction solution is purified by thin film distillation, the distillation yield is, for example, 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, for example, 80% by mass or less, preferably 70% by mass or less. It is not more than mass %. The distillation yield can be measured according to the method described in Examples below.

As described above, the isocyanurate derivative of xylylene diisocyanate is prepared.

The isocyanurate derivative of xylylene diisocyanate is an isocyanurate derivative of xylylene diisocyanate that has not been modified with alcohols (described later). In the following, an isocyanurate derivative of xylylene diisocyanate that has not been modified with alcohol is referred to as an alcohol-unmodified XDI isocyanurate derivative, and an isocyanurate derivative of xylylene diisocyanate that is modified with alcohol (described later) is used as an alcohol-modified XDI. Distinguish as an isocyanurate derivative.

The alcohol-unmodified XDI isocyanurate derivative mainly contains an isocyanurate mononuclear body. Furthermore, the alcohol-unmodified XDI isocyanurate derivative can include isocyanurate polynuclear bodies.

An isocyanurate mononuclear body is a compound in which three molecules of xylylene diisocyanate form one isocyanurate ring, and the isocyanurate ring is not bonded to another isocyanurate ring, and xylylene diisocyanate via the isocyanurate ring. Is a three-molecule body (trimer).

An isocyanurate polynuclear body is a compound in which an isocyanurate mononuclear body is bonded to another isocyanurate mononuclear body. The isocyanurate polynuclear bodies are distinguished based on the number of isocyanurate mononuclear bodies bound to each other. For example, isocyanurate binuclear bodies bound to two isocyanurate mononuclear bodies and n isocyanurate mononuclear bodies bound to each other. Examples include isocyanurate n-nuclear bodies.

In a chromatogram when such an isocyanurate derivative is subjected to gel permeation chromatography, a polystyrene-equivalent molecular weight of 400 to 1000, preferably a peak area having a peak top between 600 and 900, relative to the area of all peaks. The area ratio (hereinafter referred to as the area ratio of three molecular bodies) corresponds to the content ratio of the isocyanurate mononuclear body with respect to the total amount of the isocyanurate derivative.

The trimolecular body area ratio in the isocyanurate derivative is, for example, 25% or more, preferably 30% or more, for example, 70% or less, preferably 60% or less.

In addition, the trimolecular body area ratio is obtained by measuring the molecular weight distribution of the isocyanurate derivative by a gel permeation chromatograph (GPC) equipped with a differential refractive index detector (RID) according to an example described later. It can be calculated as the peak area ratio in the obtained chromatogram (chart) (the same applies hereinafter).

The average number of functional groups of isocyanate groups in such an isocyanurate derivative is, for example, 2 or more, preferably 2.2 or more, for example 4.0 or less, preferably 3.5 or less.

The concentration of free isocyanate groups in the isocyanurate derivative (isocyanate group concentration) is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more, for example, 40% by mass or less, It is preferably 35% by mass or less.

(1-2) Alcohol-modified xylylene diisocyanate isocyanurate derivative (alcohol-modified XDI isocyanurate derivative)
The above-mentioned isocyanurate derivative of xylylene diisocyanate is preferably modified with alcohols.

When the isocyanurate derivative is modified with alcohols, it is possible to improve the film-forming property of the polyurethane resin raw material containing blocked isocyanate, while at the same time ensuring the expansion resistance of the coating film under high-humidity conditions. You can

The alcohols preferably include aliphatic alcohols.

Examples of the aliphatic alcohol include monohydric aliphatic alcohol, divalent aliphatic alcohol, trivalent aliphatic alcohol, and tetravalent or higher aliphatic alcohol. The aliphatic alcohols can be used alone or in combination of two or more kinds.

Examples of monohydric aliphatic alcohols include linear monohydric aliphatic alcohols and branched monohydric aliphatic alcohols.

As the linear monohydric aliphatic alcohol, for example, methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, n-dodecanol (lauryl alcohol), n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, n-octadecanol (stearyl alcohol), Examples include n-nonadecanol and eicosanol.

As the branched monohydric aliphatic alcohol, for example, isopropanol (alias: isopropyl alcohol, IPA), isobutanol (alias: isobutyl alcohol, IBA), sec-butanol, tert-butanol, isopentanol, isohexanol, isoheptanol. Nol, isooctanol, 2-ethylhexanol (also known as 2-ethylhexyl alcohol, 2-EHA), isononanol, isodecanol, 5-ethyl-2-nonanol, trimethylnonyl alcohol, 2-hexyldecanol, 3,9-diethyl-6- Examples thereof include tridecanol, 2-isoheptylisoundecanol, 2-octyldodecanol, and other branched alkanols (C (carbon number, hereinafter the same) 5 to 20).

Examples of the divalent aliphatic alcohol include ethylene glycol, 1,3-propanediol (1,3-PG), 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1, Linear divalent aliphatic alcohols such as 4-dihydroxy-2-butene, diethylene glycol, triethylene glycol, dipropylene glycol, and other linear alkane (C7-20) diols, for example, 1,2-propane Diol, 1,3-butylene glycol (also known as 1,3-butanediol, 1,3-BG), 1,2-butylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol (MPD), 2,2,4-Trimethyl-1,3-pentanediol (TMPD), 3,3-dimethylolheptane, 2,6-dimethyl-1-octene-3,8-diol, and other branched alkanes (C7-). 20) branched dihydric aliphatic alcohols such as diols, for example 1,3- or 1,4-cyclohexanedimethanol and mixtures thereof, 1,3- or 1,4-cyclohexanediol and mixtures thereof, hydrogen Examples thereof include alicyclic dihydric aliphatic alcohols such as derivatized bisphenol A.

Examples of the trihydric aliphatic alcohol include glycerin and trimethylolpropane.
Examples of the tetrahydric or higher aliphatic alcohol include tetramethylolmethane, D-sorbitol, xylitol, D-mannitol and the like.

If such an aliphatic alcohol has one or more hydroxy groups in the molecule, the other molecular structure does not contain an aromatic ring in the molecule unless the excellent effects of the present invention are impaired. Other than the above, there is no particular limitation, and for example, an ester group, an ether group, a cyclohexane ring or the like can be included in the molecule.

Therefore, the aliphatic alcohol is, for example, an addition polymer of the above monovalent aliphatic alcohol and an alkylene oxide (for example, ethylene oxide, propylene oxide, etc.) (random and/or block polymer of two or more kinds of alkylene oxide). An ether group-containing monohydric aliphatic alcohol, an ester group-containing monohydric aliphatic alcohol which is an addition polymerization product of the monohydric aliphatic alcohol and a lactone (for example, ε-caprolactone, δ-valerolactone, etc.). Including.

Among such aliphatic alcohols, monohydric aliphatic alcohols and dihydric aliphatic alcohols are preferable, and branched monohydric aliphatic alcohols and branched dihydric aliphatic alcohols are more preferable. Alcohols are mentioned, particularly preferably isobutanol and 1,3-butylene glycol.

Further, when the monohydric aliphatic alcohol and the divalent aliphatic alcohol are compared, the dihydric aliphatic alcohol is more preferable. That is, the alcohol preferably contains a divalent aliphatic alcohol (branched divalent aliphatic alcohol, 1,3-butylene glycol), and more preferably a divalent aliphatic alcohol (branched dihydric alcohol). It is composed of a polyhydric alcohol and 1,3-butylene glycol).

When the alcohol that modifies the isocyanurate derivative contains a divalent aliphatic alcohol, it is possible to reliably improve the solvent resistance and weather resistance of the coating film.

Next, a method for preparing an isocyanurate derivative of xylylene diisocyanate (alcohol-modified XDI isocyanurate derivative) modified with alcohols will be described.

Examples of the method for preparing the alcohol-modified XDI isocyanurate derivative include, for example, a method of subjecting xylylene diisocyanate and an alcohol to a urethanization reaction, and then subjecting the reaction product to an isocyanurate reaction, and as described above, first, an alcohol is used. Examples include a method of preparing a non-modified XDI isocyanurate derivative and subjecting the alcohol non-modified XDI isocyanurate derivative and an alcohol to a urethane reaction.

Among such methods, preferably, a method in which xylylene diisocyanate and an alcohol are subjected to a urethanization reaction and then the reaction product is subjected to an isocyanurate reaction.

Specifically, first, xylylene diisocyanate and alcohols are blended, and xylylene diisocyanate and alcohols are subjected to a urethanization reaction at a rate where free isocyanate groups remain.

The equivalent ratio (NCO/OH) of the isocyanate group of xylylene diisocyanate to the hydroxyl group of alcohols is, for example, 3 or more, preferably 5 or more, more preferably 15 or more, for example, 600 or less, preferably 500 or less. , More preferably 200 or less, and particularly preferably 100 or less.

The mixing ratio of the alcohols is, for example, 0.05 parts by mass or more, preferably 0.10 parts by mass or more, more preferably 0.50 parts by mass or more, for example, 10 parts by mass with respect to 100 parts by mass of xylylene diisocyanate. It is not more than 8 parts by mass, preferably not more than 8 parts by mass, more preferably not more than 3 parts by mass.

The urethanization reaction is carried out, for example, in an inert gas (for example, nitrogen gas, argon gas, etc.) atmosphere.

The reaction temperature is, for example, room temperature (25° C.) or higher, preferably 40° C. or higher, for example, 100° C. or lower, preferably 90° C. or lower. The reaction pressure is, for example, atmospheric pressure. The reaction time is, for example, 0.05 hours or more, preferably 0.2 hours or more, for example, 10 hours or less, preferably 6 hours or less, more preferably 2 hours or less.

In such a urethanization reaction, the above-mentioned co-catalyst and the above-mentioned stabilizer can be added in the above-mentioned mixing ratio, and a known urethanization catalyst may be added in an appropriate ratio, if necessary.

Furthermore, in the urethanization reaction, the above-mentioned alcohols and, if necessary, an active hydrogen group-containing compound (for example, thiols, oximes, lactams, phenols, and the like, in a range that does not inhibit the excellent effect of the present invention, β diketones) can be used in combination.

As a result, the xylylene diisocyanate and the alcohols undergo a urethane reaction to produce a reaction product of the xylylene diisocyanate and the alcohols (alcohol-modified xylylene diisocyanate).

The conversion rate of the isocyanate group in such a urethanization reaction (urethane conversion rate) is, for example, 0.1% by mass or more, preferably 0.3% by mass or more, and more preferably 0.5% by mass or more, for example. , 25 mass% or less, preferably 20 mass% or less, more preferably 10 mass% or less.

As described above, the reaction liquid (reaction mixture) containing the alcohol-modified xylylene diisocyanate is prepared.

The concentration of free isocyanate groups (isocyanate group concentration) in the reaction liquid of such a urethanization reaction is, for example, 20% by mass or more, preferably 30% by mass or more, more preferably 40% by mass or more, for example, 60% by mass. It is not more than 50% by mass, preferably not more than 50% by mass.

The reaction liquid for such a urethanization reaction contains unreacted xylylene diisocyanate (alcohol unmodified xylylene diisocyanate) and alcohol-modified xylylene diisocyanate.

Then, the above-mentioned isocyanurate-forming catalyst is added to the reaction liquid of the urethanization reaction in the above-mentioned mixing ratio. Then, the xylylene diisocyanate and the alcohol-modified xylylene diisocyanate are subjected to an isocyanurate-forming reaction under the above-mentioned reaction conditions.

As a result, the alcohol-unmodified xylylene diisocyanate undergoes an isocyanurate reaction to produce an alcohol-unmodified XDI isocyanurate, and the alcohol-modified xylylene diisocyanate undergoes an isocyanurate reaction to produce an alcohol-modified XDI isocyanurate. The alcohol-modified XDI isocyanurate will be described later in detail.

The range of the isocyanurate conversion rate in such an isocyanurate-forming reaction is the same as the above-mentioned range of the isocyanurate conversion rate.

The total urethane conversion rate and isocyanurate conversion rate (conversion rate of isocyanate group (reaction rate)) is, for example, 15% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, for example. , 60 mass% or less, preferably 50 mass% or less.

As described above, the reaction liquid (reaction mixture) containing the alcohol-modified XDI isocyanurate derivative is prepared.

The concentration of free isocyanate groups (isocyanate group concentration) in the reaction liquid of such isocyanurate-forming reaction is, for example, 10% by mass or more, preferably 20% by mass or more, more preferably 25% by mass or more, for example, It is 50 mass% or less, preferably 40 mass% or less.

The reaction liquid of the isocyanurate-forming reaction contains alcohol-unmodified XDI isocyanurate and alcohol-modified XDI isocyanurate. Further, the reaction liquid of the isocyanurate-forming reaction may contain xylylene diisocyanate, alcohol-modified xylylene diisocyanate, the above-mentioned known additives and the like.

Therefore, the reaction liquid of the isocyanurate-forming reaction is preferably purified by the above-mentioned purification method. The range of the distillation yield is the same as the range of the distillation yield described above.

As described above, an isocyanurate derivative containing the alcohol-unmodified XDI isocyanurate derivative and the alcohol-modified XDI isocyanurate derivative is prepared.

The alcohol-modified XDI isocyanurate derivative is a reaction product of the above alcohol-unmodified XDI isocyanurate derivative and alcohol. The alcohol-modified XDI isocyanurate derivative includes, for example, an alcohol-modified isocyanurate mononuclear body and an alcohol-modified isocyanurate polynuclear body. In the following, the isocyanurate mononuclear body and isocyanurate polynuclear body that are not modified with alcohols are referred to as alcohol-unmodified isocyanurate mononuclear body and alcohol-unmodified isocyanurate polynuclear body.

The alcohol-modified isocyanurate mononuclear body has one isocyanurate ring to which at least one alcohol is bonded. The alcohol-modified isocyanurate mononuclear body is, for example, a compound in which an alcohol-modified xylylene diisocyanate (3-n) molecule and an x-n-molecule of xylylene diisocyanate form an isocyanurate ring, and of the xylylene diisocyanate via the isocyanurate ring. It is a trimolecular body. In addition, n is an integer of 0-2.

The alcohol-modified isocyanurate polynuclear body is a compound that has two or more isocyanurate rings and at least one alcohol is bonded to these isocyanurate rings. The alcohol-modified isocyanurate polynuclear body is, for example, a compound in which an alcohol-modified isocyanurate mononuclear body is bonded to at least one alcohol-modified isocyanurate mononuclear body or an alcohol-unmodified isocyanurate mononuclear body.

More specifically, when the alcohol is a monohydric aliphatic alcohol, examples of the alcohol-modified isocyanurate polynuclear body include a direct bond type alcohol-modified isocyanurate polynuclear body.

The direct bond-type alcohol-modified isocyanurate polynuclear body is a compound in which the isocyanate group of the alcohol-modified isocyanurate mononuclear body also serves as another alcohol-modified isocyanurate mononuclear body or an alcohol-unmodified isocyanurate mononuclear body. That is, in the direct bond type alcohol-modified isocyanurate polynuclear body, the isocyanurate ring of the alcohol-modified isocyanurate mononuclear body and the isocyanurate ring of the alcohol-modified isocyanurate mononuclear body or the alcohol-unmodified isocyanurate mononuclear body are 1 The two xylylene diisocyanates are linked through the skeleton.

When the alcohol is a dihydric aliphatic alcohol, examples of the alcohol-modified isocyanurate polynuclear body include, for example, a direct bond-type alcohol-modified isocyanurate polynuclear body and a cross-linked alcohol-modified isocyanurate binuclear body similar to the above. Can be mentioned.

The crosslinked alcohol-modified isocyanurate binuclear compound is a divalent aliphatic compound in which the isocyanate group of the alcohol-modified isocyanurate mononuclear body and the isocyanate group of the alcohol-modified isocyanurate mononuclear body or the alcohol-unmodified isocyanurate mononuclear body It is a compound that reacts with and binds to each of the hydroxyl groups of alcohol. That is, the crosslinked alcohol-modified isocyanurate binuclear body is obtained by combining an alcohol-modified isocyanurate mononuclear body with an alcohol-modified isocyanurate mononuclear body or an alcohol-unmodified isocyanurate mononuclear body through a divalent aliphatic alcohol. Are connected.

Further, in the above-mentioned urethane-forming reaction and/or isocyanurate-forming reaction, alcohol-modified xylylene diisocyanate and/or alcohol-modified XDI isocyanurate derivative reacts with xylylene diisocyanate and/or alcohol-modified xylylene diisocyanate to give allophanate. May be generated. In this case, the isocyanurate derivative comprises allophanate.

The trimolecular area ratio of the isocyanurate derivative including the alcohol-modified XDI isocyanurate derivative is the content of the alcohol-unmodified isocyanurate mononuclear body and the content of the alcohol-modified isocyanurate mononuclear body with respect to the total amount of the isocyanurate derivative. Corresponds to the total content of the above-mentioned allophanate consisting of 3 molecules.

The trimolecular body area ratio in the isocyanurate derivative including the alcohol-modified XDI isocyanurate derivative is, for example, 30% or more, preferably 35% or more, for example, 60% or less, preferably 55% or less, more preferably 52. % Or less.

The average number of functional groups of the isocyanate group in the isocyanurate derivative including the alcohol-modified XDI isocyanurate derivative is, for example, 2 or more, preferably 2.2 or more, for example, 4.0 or less, preferably 3.5 or less. is there.

The concentration of free isocyanate groups (isocyanate group concentration) in isocyanurate derivatives including alcohol-modified XDI isocyanurate derivatives is, for example, 5% by mass or more, preferably 10% by mass or more, more preferably 15% by mass or more. For example, it is 40% by mass or less, preferably 35% by mass or less, more preferably 25% by mass or less.

The amount of modification of the alcohols in the isocyanurate derivative including the alcohol-modified XDI isocyanurate derivative is, for example, 0.1% by mass or more, preferably 0.2% by mass or more, more preferably 0.7% by mass or more. For example, it is 20 mass% or less, preferably 15 mass% or less, more preferably 10.0 mass% or less. The modified amount of alcohols is the ratio (mass ratio) of the mass parts of alcohols to the mass parts of xylylene diisocyanate in the isocyanurate derivative, and can be measured in accordance with the method described in Examples below. Furthermore, the modified amount of alcohols can also be calculated by ¹ H-NMR measurement as described in paragraph [0086] of Japanese Patent No. 6161788, for example.

When the amount of modification of the alcohols is not less than the above lower limit, it is possible to improve the film-forming property of the polyurethane resin raw material containing the blocked isocyanate, while ensuring the expansion resistance of the coating film under high humidity conditions. be able to. When the amount of modification of the alcohols is not more than the above upper limit, the weather resistance of the coating film can be surely improved, while the expansion resistance of the coating film under high humidity conditions can be surely improved.

In addition, a compound containing a sulfonamide group can be added to the isocyanurate derivative at an appropriate ratio, if necessary.

Examples of the compound containing a sulfonamide group include aromatic sulfonamides and aliphatic sulfonamides. The compounds containing sulfonamide groups can be used alone or in combination of two or more kinds.

Examples of aromatic sulfonamides include benzenesulfonamide, dimethylbenzenesulfonamide, sulfanilamide, o- and p-toluenesulfonamide, hydroxynaphthalenesulfonamide, naphthalene-1-sulfonamide, naphthalene-2-sulfonamide, and m. -Nitrobenzenesulfonamide, p-chlorobenzenesulfonamide and the like.

Examples of the aliphatic sulfonamides include methanesulfonamide, N,N-dimethylmethanesulfonamide, N,N-dimethylethanesulfonamide, N,N-diethylmethanesulfonamide, N-methoxymethanesulfonamide, and N-dodecyl. Examples thereof include methanesulfonamide, N-cyclohexyl-1-butanesulfonamide, 2-aminoethanesulfonamide and the like.

The isocyanurate derivative can be prepared as a diluted solution of the isocyanurate derivative by diluting it with an organic solvent, if necessary.

Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; nitriles such as acetonitrile; alkyl esters such as methyl acetate, ethyl acetate, butyl acetate, and isobutyl acetate; for example, n-hexane. , N-heptane, aliphatic hydrocarbons such as octane, for example, cyclohexane, alicyclic hydrocarbons such as methylcyclohexane, for example, aromatic hydrocarbons such as toluene, xylene, ethylbenzene, for example, methyl cellosolve acetate, Glycol ether esters such as ethyl cellosolve acetate, methyl carbitol acetate, ethyl carbitol acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropionate Ethers such as diethyl ether, tetrahydrofuran and dioxane, for example, halogenated aliphatic hydrocarbons such as methyl chloride, methylene chloride, chloroform, carbon tetrachloride, methyl bromide, methylene iodide and dichloroethane, for example, Examples include polar aprotons such as N-methylpyrrolidone, dimethylformamide, N,N′-dimethylacetamide, dimethylsulfoxide, and hexamethylphosphonylamide.

(1-2) Polyoxyethylene Compound The polyoxyethylene compound has at least three continuous ethylene oxide groups and an active hydrogen group capable of reacting with an isocyanate group (for example, a hydroxyl group or an amino group).

Examples of the polyoxyethylene compound include a polyoxyethylene group-containing polyol, a polyoxyethylene group-containing polyamine, a single-end blocked polyoxyethylene glycol, and a single-end blocked polyoxyethylenediamine.

Examples of the polyoxyethylene group-containing polyol include polyoxyethylene glycol, polyoxyethylene triol, random and/or block copolymers of ethylene oxide and propylene oxide (for example, polyoxypropylene polyoxyethylene copolymer diol or triol, Oxypropylene polyoxyethylene block polymer diol or triol, Pluronic type polypropylene glycol or triol obtained by addition-polymerizing ethylene oxide to the end of polypropylene glycol).

Examples of polyoxyethylene group-containing polyamines include polyoxyalkylene ether diamines such as polyoxyethylene ether diamine.

Examples of the one-end blocked polyoxyethylene glycol include alkoxy polyethylene glycol (poly(oxyethylene)alkyl ether) having one end blocked with an alkyl group having 1 to 20 carbon atoms, and specifically, methoxy polyethylene glycol. (Poly(oxyethylene) methyl ether), ethoxy polyethylene glycol (poly(oxyethylene) ethyl ether) and the like.

Examples of the one-end blocked polyoxyethylenediamine include polyoxyethylenediamine having one end blocked with an alkoxy group having 1 to 20 carbon atoms.

Such polyoxyethylene compounds can be used alone or in combination of two or more kinds.

The polyoxyethylene compound is preferably a polyoxyethylene group-containing polyol, and one end-blocked polyoxyethylene glycol, more preferably one-end blocked polyoxyethylene glycol, and particularly preferably an alkoxy polyethylene. Glycols (poly(oxyethylene)alkyl ethers) are mentioned, particularly preferably methoxy polyethylene glycol.

The number average molecular weight of such a polyoxyethylene compound is, for example, 200 or more, preferably 300 or more, for example, 2000 or less, preferably 1000 or less. The number average molecular weight of the polyoxyethylene compound can be measured by gel permeation chromatography.

(1-3) Preparation of Polyisocyanate Next, preparation of polyisocyanate will be described.

As described above, the polyisocyanate contains the reaction product of the isocyanurate derivative and the polyoxyethylene compound (hydrophilic isocyanurate derivative).

In order to prepare a polyisocyanate containing a hydrophilic isocyanurate derivative, the above-mentioned isocyanurate derivative and the above-mentioned polyoxyethylene compound are reacted with each other at a ratio where free isocyanate groups remain.

The equivalent ratio of the active hydrogen group of the polyoxyethylene compound to the free isocyanate group of the isocyanurate derivative (active hydrogen group/NCO) is, for example, 0.01 or more, preferably 0.05 or more, for example, 0.30. Hereafter, it is preferably 0.20 or less.

The mixing ratio of the polyoxyethylene compound is, for example, 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 25 parts by mass or more, for example, 70 parts by mass or less, with respect to 100 parts by mass of the isocyanurate derivative. It is preferably 60 parts by mass or less, and more preferably 55 parts by mass or less.

The reaction between the isocyanurate derivative and the polyoxyethylene compound is carried out, for example, in an inert gas (for example, nitrogen gas, argon gas, etc.) atmosphere, for example, in the presence of the above-mentioned organic solvent.

Among such organic solvents, glycol ether esters are preferable, and propylene glycol monomethyl ether acetate is more preferable.

The addition ratio of the organic solvent is, for example, 1 part by mass or more, preferably 10 parts by mass or more, for example, 100 parts by mass or less, preferably 50 parts by mass or less, and more preferably 100 parts by mass with respect to 100 parts by mass of the isocyanurate derivative. , 30 parts by mass or less.

The reaction temperature is, for example, 50° C. or higher, preferably 70° C. or higher, for example, 150° C. or lower, preferably 110° C. or lower. The reaction pressure is, for example, atmospheric pressure. The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, for example, 120 hours or less, preferably 72 hours or less.

The completion of the reaction can be determined, for example, by the fact that the amount of isocyanate measured by the titration method does not change.

Note that the isocyanurate derivative and the polyoxyethylene compound can be reacted in the absence of a solvent.

As a result, the isocyanate group of the xylylene diisocyanate isocyanurate derivative (alcohol-unmodified XDI isocyanurate derivative and/or alcohol-modified XDI isocyanurate derivative) reacts with the active hydrogen group of the polyoxyethylene compound to form two or more groups. A hydrophilic isocyanurate derivative in which the free isocyanate groups of the above remain is produced.

As described above, the polyisocyanate containing the hydrophilic isocyanurate derivative is prepared.

When the isocyanurate derivative contains the alcohol-unmodified XDI isocyanurate derivative and does not contain the alcohol-modified XDI isocyanurate derivative, the hydrophilic isocyanurate derivative is a reaction product of the alcohol-unmodified XDI isocyanurate derivative and the polyoxyethylene compound. (Alcohol-denatured hydrophilic isocyanurate derivative) is not included, and the reaction product of the alcohol-modified XDI isocyanurate derivative and the polyoxyethylene compound (alcohol-modified hydrophilic isocyanurate derivative) is not included. In this case, the polyisocyanate can contain, for example, an unreacted alcohol-unmodified XDI isocyanurate derivative in addition to the alcohol-unmodified hydrophilic isocyanurate derivative.

When the isocyanurate derivative includes an alcohol-unmodified XDI isocyanurate derivative and an alcohol-modified XDI isocyanurate derivative, the hydrophilic isocyanurate derivative is an alcohol-unmodified hydrophilic isocyanurate derivative and an alcohol-modified hydrophilic isocyanurate derivative. including. In this case, the polyisocyanate may be, for example, an unreacted alcohol-unmodified XDI isocyanurate derivative and/or an unreacted alcohol-modified XDI isocyanurate in addition to the alcohol-unmodified hydrophilic isocyanurate derivative and the alcohol-modified hydrophilic isocyanurate derivative. Derivatives can be included.

The content ratio (in terms of solid content) of the hydrophilic isocyanurate derivative in the polyisocyanate is, for example, 20% by mass or more, preferably 30% by mass or more, for example, 95% by mass or less, and preferably 90% by mass or less.

The average number of functional groups of free isocyanate groups in the polyisocyanate is, for example, 2 or more, preferably 2.2 or more, such as 4.0 or less, preferably 3.5 or less.

The isocyanate group concentration (in terms of solid content) of the polyisocyanate is, for example, 5% by mass or more, preferably 7% by mass or more, for example, 30% by mass or less, preferably 25% by mass or less, more preferably 20% by mass. It is as follows.

The content of ethylene oxide group in the polyisocyanate (as solid content) is 15% by mass or more, preferably 18% by mass or more and 30% by mass or less, preferably 25% by mass or less, and more preferably 22% by mass or less. is there. The content of ethylene oxide group in the polyisocyanate can be calculated according to the method described in Examples below.

When the content of the ethylene oxide group in the polyisocyanate is within the above range, it is possible to secure excellent water dispersibility and to impart excellent swelling resistance under high humidity conditions to the coating film.

The amount of modification of alcohols in the polyisocyanate is, for example, 0.07 mass% or more, preferably 0.14 mass% or more, for example 6.0 mass% or less, preferably 5.4 mass% or less. is there. The modified amount of alcohols in polyisocyanate can be calculated by the following formula.

Modified amount of alcohols in polyisocyanate (% by mass) = Modified amount of alcohols in isocyanurate derivative (% by mass) x Charge amount of polyoxyethylene compound (mass part) / Charge amount of hydrophilic isocyanurate derivative (mass part) ) X 100
Further, in general, it can also be calculated by ¹ H-NMR measurement in the same manner as the modified amount of alcohols in the isocyanurate derivative.

(2) Blocking agent The blocking agent has an active group capable of reacting with an isocyanate group, and reacts with the free isocyanate group of the polyisocyanate to form a latent isocyanate group. That is, the blocked isocyanate contains a latent isocyanate group blocked by the blocking agent.

Examples of the blocking agent include the first blocking agent and the second blocking agent described in JP-A-2017-82208. Specifically, guanidine-based compounds, imidazole-based compounds, alcohol-based compounds, phenol-based compounds, Active methylene compounds, amine compounds, imine compounds, oxime compounds, carbamic acid compounds, urea compounds, acid amide (lactam) compounds, acid imide compounds, triazole compounds, pyrazole compounds, mercaptan compounds Examples thereof include compounds, bisulfites, imidazoline compounds, and pyrimidine compounds. The blocking agents can be used alone or in combination of two kinds.

Examples of the guanidine-based compound include guanidine, for example, 1-alkylguanidine such as 1-methylguanidine, 1-arylguanidine such as 1-phenylguanidine, and 1,3-dialkyl such as 1,3-dimethylguanidine. Guanidine, for example, 1,3-diphenylguanidine, 1,3-di(o-tolyl)-guanidine and other 1,3-diarylguanidines, for example, 1,1-dimethylguanidine, 1,1-diethylguanidine and the like 1 ,1-Dialkylguanidines such as 1,2,3-trimethylguanidine 1,2,3-trialkylguanidines such as 1,2,3-triphenylguanidine 1,2,3-triarylguanidines , 1,1,3,3-tetraalkylguanidines such as 1,1,3,3-tetramethylguanidine, eg 1,5,7-triazabicyclo[4.4.0]deca-5. En is mentioned.

As the imidazole compound, for example, imidazole, benzimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2- Amine-imidazole and the like can be mentioned.

Examples of alcohol compounds include methanol, ethanol, 2-propanol, n-butanol, s-butanol, 2-ethylhexyl alcohol, 1- or 2-octanol, cyclohexyl alcohol, ethylene glycol, benzyl alcohol, 2,2,2. 2-trifluoroethanol, 2,2,2-trichloroethanol, 2-(hydroxymethyl)furan, 2-methoxyethanol, methoxypropanol, 2-ethoxyethanol, n-propoxyethanol, 2-butoxyethanol, 2-ethoxyethoxy. Ethanol, 2-ethoxybutoxyethanol, butoxyethoxyethanol, 2-butoxyethylethanol, 2-butoxyethoxyethanol, N,N-dibutyl-2-hydroxyacetamide, N-hydroxysuccinimide, N-morpholine ethanol, 2,2-dimethyl Examples thereof include -1,3-dioxolane-4-methanol, 3-oxazolidineethanol, 2-hydroxymethylpyridine, furfuryl alcohol, 12-hydroxystearic acid, triphenylsilanol, and 2-hydroxyethyl methacrylate.

Examples of the phenol compound include phenol, cresol, ethylphenol, n-propylphenol, isopropylphenol, n-butylphenol, s-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, n-. Nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol, di-s-butylphenol, di-t-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n- Nonylphenol, nitrophenol, bromophenol, chlorophenol, fluorophenol, dimethylphenol, styrenated phenol, methyl salicylate, methyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, 2-ethylhexyl hydroxybenzoate, 4-[ (Dimethylamino)methyl]phenol, 4-[(dimethylamino)methyl]nonylphenol, bis(4-hydroxyphenyl)acetic acid, 2-hydroxypyridine, 2- or 8-hydroxyquinoline, 2-chloro-3-pyridinol, pyridine -2-thiol etc. are mentioned.

As the active methylene compound, for example, Meldrum's acid, for example, dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-t-butyl malonate, di2-ethylhexyl malonate, methyl n-butyl malonate, Ethyl n-butyl malonate, methyl s-butyl malonate, ethyl s-butyl malonate, methyl t-butyl malonate, ethyl t-butyl malonate, diethyl methyl malonate, dibenzyl malonate, diphenyl malonate, malonic acid Dialkyl malonates such as benzylmethyl, ethylphenyl malonate, t-butylphenyl malonate and isopropylidene malonate, for example, methyl acetoacetate, ethyl acetoacetate, n-propyl acetoacetate, isopropyl acetoacetate, n-butyl acetoacetate. , T-butyl acetoacetate, benzyl acetoacetate, alkyl acetoacetate such as phenyl acetoacetate, for example, 2-acetoacetoxyethyl methacrylate, acetylacetone, ethyl cyanoacetate and the like.

Examples of amine compounds include dibutylamine, diphenylamine, aniline, N-methylaniline, carbazole, bis(2,2,6,6-tetramethylpiperidinyl)amine, di-n-propylamine, diisopropylamine, isopropyl. Ethylamine, 2,2,4- or 2,2,5-trimethylhexamethyleneamine, N-isopropylcyclohexylamine, dicyclohexylamine, bis(3,5,5-trimethylcyclohexyl)amine, piperidine, 2,6-dimethylpiperidine , T-butylmethylamine, t-butylethylamine, t-butylpropylamine, t-butylbutylamine, t-butylbenzylamine, t-butylphenylamine, 2,2,6-trimethylpiperidine, 2,2,6. 6-tetramethylpiperidine, (dimethylamino)-2,2,6,6-tetramethylpiperidine, 2,2,6,6-tetramethyl-4-piperidine, 6-methyl-2-piperidine, 6-aminocaproic acid And so on.

Examples of the imine compound include ethyleneimine, polyethyleneimine, 1,4,5,6-tetrahydropyrimidine and the like.

Examples of the oxime compound include formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, diacetylmonooxime, benzophenooxime, 2,2,6,6-tetramethylcyclohexanone oxime, diisopropylketone oxime, Methyl t-butyl ketone oxime, diisobutyl ketone oxime, methyl isobutyl ketone oxime, methyl isopropyl ketone oxime, methyl 2,4-dimethylpentyl ketone oxime, methyl 3-ethylheptyl ketone oxime, methyl isoamyl ketone oxime, n-amyl ketone oxime 2,2,4,4-tetramethyl-1,3-cyclobutanedione monooxime, 4,4′-dimethoxybenzophenone oxime, 2-heptanone oxime and the like.

Examples of the carbamic acid compound include phenyl N-phenylcarbamate.

Examples of the urea compound include urea, thiourea, ethylene urea and the like.

Examples of the acid amide (lactam) compound include acetanilide, N-methylacetamide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, pyrrolidone, 2,5-piperazinedione, laurolactam and the like. ..

Examples of the acid imide-based compound include succinimide, maleic acid imide, and phthalimide.

Examples of the triazole-based compound include 1,2,4-triazole and benzotriazole.

Examples of the pyrazole-based compound include pyrazole, 3,5-dimethylpyrazole, 3,5-diisopropylpyrazole, 3,5-diphenylpyrazole, 3,5-di-t-butylpyrazole, 3-methylpyrazole, 4-benzyl- 3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole and the like can be mentioned.

Examples of the mercaptan compound include butyl mercaptan, dodecyl mercaptan, and hexyl mercaptan.

Examples of the bisulfite include sodium bisulfite and the like.

Examples of the imidazoline compound include 2-methylimidazoline and 2-phenylimidazoline.

Examples of the pyrimidine compound include 2-methyl-1,4,5,6-tetrahydropyrimidine.

Among such blocking agents, preferred are oxime-based compounds and pyrazole-based compounds, more preferred are methylethylketoxime and 3,5-dimethylpyrazole, and particularly preferred is 3,5-dimethylpyrazole. Are listed.

That is, the blocking agent preferably contains a pyrazole-based compound and/or an oxime-based compound, more preferably 3,5-dimethylpyrazole and/or methylethylketoxime, and particularly preferably 3,5-dimethylpyrazole. Including. Further, the blocking agent preferably consists of a pyrazole compound (3,5-dimethylpyrazole) and/or an oxime compound (methylethylketoxime).

When the blocking agent contains a pyrazole-based compound and/or an oxime-based compound, excellent mechanical properties, solvent resistance, weather resistance, and swelling resistance under high humidity conditions can be more reliably imparted to the coating film. In particular, when the blocking agent contains a pyrazole-based compound, the weather resistance of the coating film and the swelling resistance under high humidity conditions can be further improved.

The dissociation temperature of the blocking agent is, for example, 150° C. or lower, preferably 140° C. or lower, for example 60° C. or higher. The dissociation temperature of the blocking agent can be measured by the following method (the same applies hereinafter).

The blocked isocyanate is applied to a silicon wafer, and the temperature at which the isocyanate group is regenerated is observed by IR measurement while heating. When the regenerated isocyanate group cannot be observed, the blocking agent is mixed with a known polyol, the mixture is applied to a silicon wafer, and the temperature at which the hydroxyl group of the polyol reacts is observed by IR measurement while heating. The dissociation temperature of can be measured.

(3) Production of Blocked Isocyanate Next, production of blocked isocyanate will be described.

To produce a blocked isocyanate, the above polyisocyanate is reacted with the above blocking agent.

The equivalent ratio of the active group capable of reacting with the isocyanate group in the blocking agent to the isocyanate group of the polyisocyanate (active group/isocyanate group) is, for example, 0.2 or more, preferably 0.5 or more, for example, 1.5. It is preferably 1.2 or less, more preferably 1.1 or less.

The reaction between the polyisocyanate and the blocking agent is carried out, for example, in an inert gas (for example, nitrogen gas or argon gas) atmosphere.

The reaction temperature is, for example, 0° C. or higher, preferably 20° C. or higher, for example, 80° C. or lower, preferably 60° C. or lower. The reaction pressure is, for example, atmospheric pressure. The reaction time is, for example, 0.5 hour or more, preferably 1.0 hour or more, for example, 24 hours or less, preferably 12 hours or less.

This produces latent isocyanate groups blocked by the blocking agent.

When two or more blocking agents are used in combination, two or more blocking agents may be reacted with polyisocyanate at the same time, or two second blocking agents may be reacted with polyisocyanate sequentially.

Further, the completion of the reaction can be judged by, for example, adopting an infrared spectroscopic analysis method and confirming the disappearance or decrease of the isocyanate group.

Further, the above reaction may be performed without a solvent, for example, in the presence of a solvent. Examples of the solvent include the above-mentioned organic solvents and plasticizers. The solvent can be used alone or in combination of two or more kinds.

Examples of the plasticizer include the plasticizers described in paragraphs [0109] to [0117] of JP-A-2017-82208. The plasticizers can be used alone or in combination of two or more kinds.

As described above, a blocked isocyanate in which the isocyanate group of polyisocyanate is blocked by the blocking agent is prepared.

When the polyisocyanate contains the alcohol-unmodified hydrophilic isocyanurate derivative and does not contain the alcohol-modified hydrophilic isocyanurate derivative, the blocked isocyanate contains the reaction product of the alcohol-unmodified hydrophilic isocyanurate derivative and the blocking agent.

When the polyisocyanate contains an alcohol-unmodified hydrophilic isocyanurate derivative and an alcohol-modified hydrophilic isocyanurate derivative, the blocked isocyanate is a reaction product of the alcohol-unmodified hydrophilic isocyanurate derivative and the blocking agent, and an alcohol-modified hydrophilic Reactive isocyanurate derivative and a reaction product of a blocking agent.

The blocked isocyanate is a water-dispersible blocked isocyanate and does not contain water or an organic solvent.

The content of ethylene oxide group (in terms of solid content) in such blocked isocyanate is, for example, 11.3% by mass or more, preferably 13.5% by mass or more, for example, 22.5% by mass or less, and preferably 18%. It is not more than 8% by mass. The content of ethylene oxide group in the blocked isocyanate can be calculated by the following formula.

Content of ethylene oxide group in blocked isocyanate (mass %)=content of polyoxyethylene compound in hydrophilic polyisocyanurate derivative (mass %)×charge of hydrophilic polyisocyanurate derivative (mass part)/[hydrophilic poly Charge amount of isocyanurate derivative (mass part)+charge amount of blocking agent (mass part)]×100.

The modified amount of the alcohols in the blocked isocyanate is, for example, 0.075 mass% or more, preferably 0.13 mass% or more, for example 4.5 mass% or less, preferably 4.1 mass% or less. is there. The modified amount of alcohols in the blocked isocyanate can be calculated by the following formula.

Denaturation rate of alcohols in blocked isocyanate (mass %)=content of alcohols in hydrophilic polyisocyanurate derivative (mass %)×charge of hydrophilic polyisocyanurate derivative (mass part)/[hydrophilic polyisocyanurate Charge amount of derivative (mass part)+charge amount of blocking agent (mass part)]×100.

<Polyurethane paint>
Such a blocked isocyanate can be used as a known resin raw material such as a polyurethane resin raw material, and is preferably used as a two-component polyurethane resin raw material.

The two-component polyurethane resin raw material includes an agent A as a polyisocyanate component containing the above-mentioned blocked isocyanate and an agent B as a polyol component. The two-component polyurethane resin raw material is prepared by mixing the agent A (curing agent) and the agent B (main agent), which are separately prepared, immediately before use.

The polyisocyanate component is prepared by dispersing the above-mentioned blocked isocyanate in water. That is, the polyisocyanate component contains the above-mentioned blocked isocyanate and water.

The content ratio of the blocked isocyanate in the polyisocyanate component is appropriately changed, for example, 1 mass% or more, preferably 5 mass% or more, more preferably 20 mass% or more, for example, 60 mass% or less, preferably , 50 mass% or less.

When a macropolyol (described later) is dispersed in water in the polyol component, the blocked isocyanate may not be dispersed in water in the polyisocyanate component.

The polyol component contains, for example, a macropolyol, and is preferably prepared by dispersing the macropolyol in water. That is, the polyol component contains macropolyol and water.

The macropolyol is a high molecular weight polyol having a number average molecular weight of 250 or more, preferably 400 or more, for example 10,000 or less.

Examples of macropolyols include polyester polyols, vegetable oil-based polyester polyols, polycaprolactone polyols, polyether polyols, polycarbonate polyols, acrylic polyols, urethane-modified polyols, and the like. The macropolyols can be used alone or in combination of two or more.

As a polyester polyol, for example, esterification of a polybasic acid (eg, adipic acid, sebacic acid, phthalic acid, isophthalic acid, etc.) with a low molecular weight polyol (eg, ethylene glycol, propylene glycol, butanediol, neopentyl glycol, etc.) Examples include reactants.

As the vegetable oil-based polyester polyol, for example, a hydroxyl group-containing vegetable oil fatty acid (for example, castor oil fatty acid containing ricinoleic acid, hydrogenated castor oil fatty acid containing 12-hydroxystearic acid, etc.) using the above-mentioned low molecular weight polyol as an initiator, etc. Examples thereof include condensation products of hydroxycarboxylic acids.

Examples of polycaprolactone polyols include ring-opening polymers of lactones (for example, ε-caprolactone, γ-valerolactone, etc.) that use the above-mentioned low molecular weight polyol as an initiator.

Examples of the polyether polyols include ring-opening polymerization products of alkylene oxides using the above-mentioned low molecular weight polyol as an initiator.

Examples of the polycarbonate polyol include ring-opening polymerization products of ethylene carbonate using the above-mentioned low molecular weight polyol as an initiator.

Examples of the acrylic polyol include a copolymer of a hydroxyl group-containing acrylate and a copolymerizable vinyl monomer copolymerizable with the hydroxyl group-containing acrylate.

The urethane-modified polyol is, for example, a reaction product of the above-described macropolyol and a known polyisocyanate, and includes, for example, polyester type polyurethane polyol, polyether type polyurethane polyol, polycarbonate type polyurethane polyol, and polyacrylic type. Examples thereof include polyurethane polyols and polyester polyether type polyurethane polyols.

Among such macropolyols, acrylic polyol is preferable.

Further, if necessary, one or both of an isocyanate component (curing agent) and a polyol compound (main agent) may be added, for example, a reaction solvent, a catalyst, an epoxy resin, a coating property improving agent, a leveling agent, a defoaming agent. , Stabilizers such as antioxidants and UV absorbers, thickeners, anti-settling agents, plasticizers, surfactants, pigments, fillers, organic or inorganic fine particles, and additives such as mildew proofing agents should be added as appropriate. You can The blending amount of the additive is appropriately determined depending on its purpose and use.

In such a two-component polyurethane resin raw material, a polyisocyanate component (curing agent) and a polyol component (main ingredient) are blended when used.

The compounding ratio of the polyisocyanate component (curing agent) and the polyol component (main agent) is, for example, the equivalent ratio of the latent isocyanate group of the blocked isocyanate to the hydroxyl group of the macropolyol (latent isocyanate group/hydroxyl group) is, for example, 0.1. The above ratio is preferably 0.5 or more, for example, 5 or less, and preferably 3 or less.

Then, the mixture of the polyisocyanate component and the polyol component is applied to an object by a known coating method (for example, spray coating, dip coating, spin coating, rotary atomization coating, curtain coating coating, etc.). It is processed and dried to form a coating film. Then, the coating film is cured by heating and aged if necessary.

The heating temperature is, for example, 60° C. or higher, preferably 80° C. or higher, for example 150° C. or lower, preferably 130° C. or lower.

As described above, the coating film (cured coating film, polyurethane resin) is formed from the two-component polyurethane resin raw material containing the blocked isocyanate. Such a coating film is particularly excellent in swelling resistance under high humidity conditions. The high humidity condition means that the relative humidity at a predetermined temperature is 70% or more.

Therefore, the two-component polyurethane resin raw material is preferably used particularly for applications exposed to high humidity conditions. More specifically, the two-component polyurethane resin material is used as a coating material (for example, food packaging ink coating material), an adhesive material (for example, food packaging film or paper, plastic bottles, cans, bottles, etc.). Adhesive raw materials for packaging materials, etc.) and the like.

<Effect>
The above-mentioned blocked isocyanate is a blocked isocyanate in which polyisocyanate is blocked by a blocking agent, wherein the polyisocyanate includes an isocyanurate derivative of xylylene diisocyanate and a reaction product of a polyoxyethylene compound, and ethylene oxide in the polyisocyanate. The content of the group is within the above range.

Therefore, while ensuring excellent water dispersibility, it is possible to impart swelling resistance under high humidity conditions to the coating film (polyurethane resin).

The isocyanurate derivative of xylylene diisocyanate is preferably modified with alcohols.

Therefore, while improving the water dispersibility of the blocked isocyanate, it is possible to improve the expansion resistance of the coating film (polyurethane resin) under high humidity conditions.

The amount of modification of alcohols in the isocyanurate derivative is preferably at least the above lower limit. Therefore, the film-forming property of the polyurethane resin raw material containing the blocked isocyanate can be improved, while the expansion resistance of the coating film (polyurethane resin) under high humidity conditions can be reliably improved.

The amount of modification of alcohols in the isocyanurate derivative is preferably the above upper limit or less. Therefore, while the weather resistance of the coating film (polyurethane resin) can be surely improved, the expansion resistance of the coating film (polyurethane resin) under high humidity conditions can be surely improved.

The alcohol that modifies the isocyanurate derivative preferably contains a divalent aliphatic alcohol. Therefore, the solvent resistance and weather resistance of the coating film (polyurethane resin) can be more surely improved.

Further, the blocking agent preferably contains a pyrazole compound and/or an oxime compound. Therefore, excellent mechanical properties, solvent resistance, weather resistance, and expansion resistance under high humidity conditions can be more reliably imparted to the coating film (polyurethane resin).

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto. Specific numerical values such as a blending ratio (content ratio), physical property values, and parameters used in the following description are described in the above-mentioned "Description of Embodiments", and a corresponding blending ratio (content ratio). ), physical property values, parameters, etc., may be replaced by the upper limit values (values defined as “below” or “less than”) or lower limit values (values defined as “greater than” or “exceeded”). it can. In addition, "part" and "%" are based on mass unless otherwise specified.

In addition, the measurement methods and calculation methods used in each example and each comparative example will be described below.

<Distillation yield>
For the distillation yield of the isocyanurate derivative, the mass of the reaction liquid (pre-distillation liquid) and the mass of the isocyanurate derivative (post-distillation liquid) are measured, and the ratio of the mass of the isocyanurate derivative to the mass of the reaction liquid is calculated by the following formula. I asked for it.
Distillation yield of isocyanurate derivative (mass %)=(mass of isocyanurate derivative (mass part)/mass of reaction liquid (mass part))×100
<Modification amount of alcohols (alcohol modification amount)>
The ratio (parts by mass) of alcohols in the reaction solution was calculated as the mass of alcohols to the mass of 100 parts by mass of xylylene diisocyanate. Further, the amount of alcohol modification in the isocyanurate derivative (the amount of alcohol modification of the isocyanurate derivative) was calculated by the following formula.
Alcohol modification amount of isocyanurate derivative (mass %)=(ratio of alcohols in reaction liquid (mass part)/distillation yield (mass %))×100
<Isocyanate group concentration and conversion rate of isocyanate group (reaction rate)>
The isocyanate group concentrations of the charging solution, the reaction solution, and the isocyanurate derivative were measured according to the n-dibutylamine method of JIS K-1556 (2006). Further, the conversion rate (reaction rate) of the isocyanate group was obtained by calculating the reduction rate of the isocyanate group concentration of the reaction solution or isocyanurate derivative with respect to the isocyanate group concentration of the charging solution.

The conversion rate of the isocyanate group after the blending of the alcohols and before the blending of the isocyanurate-forming catalyst is the urethane conversion rate, and the conversion rate of the isocyanate group after the blending of the isocyanurate-forming catalyst is the isocyanurate conversion rate.

<Area ratio of 3 molecular bodies>
A sample of an isocyanurate derivative was subjected to gel permeation chromatography (GPC) measurement, and in the obtained chromatogram (chart), the area of the peak having a polystyrene-equivalent molecular weight of 400 to 1000 as the peak top, relative to the area of all peaks. From the ratio, the trimolecular body area ratio was obtained.

In addition, in the chromatogram (chart) obtained by the following device, the trimolecular body area ratio is the area of the peak area having the peak top between the retention times of 26.8 minutes and 27.1 minutes with respect to the area of all peaks. It is also a rate.

In the GPC measurement, about 0.04 g of a sample was collected, methylurethane-ized with methanol, excess methanol was removed, and 10 mL of tetrahydrofuran was added and dissolved. Then, the obtained solution was subjected to GPC measurement under the following conditions.
(1) Analytical device: Alliance (manufactured by Waters)
(2) Pump: Alliance 2695 (manufactured by Waters)
(3) Detector: 2414 type differential refraction detector (manufactured by Waters)
(4) Eluent: Tetrahydrofuran
(5) Separation column: Plgel GUARD + Plgel 5 μm mixed-C x 3 (50 x 7.5 mm, 300 x 7.5 mm) manufacturer; Polymer Laboratories, product number; PL1110-6500.
(6) Measurement temperature: 40°C
(7) Flow rate: 1 mL/min
(8) Sample injection amount and injection concentration: 100 μL, 1 mg/mL
(9) Analysis device: EMPOWER data processing device (manufactured by Waters)
・System correction (1) Reference substance name: Polystyrene
(2) Method of preparing calibration curve: Using TSK standard Polystyrene manufactured by TOSOH having different molecular weights, a graph of retention time (retention time) and molecular weight is prepared.

<Ethylene oxide group content in reaction product of polyisocyanate derivative and polyoxyethylene compound>
The ethylene oxide group content in the reaction product was calculated by the following formula.
Ethylene oxide group content (mass %)=charge of polyoxyethylene compound (mass part)/[charge of polyisocyanate derivative (mass part)+charge of polyoxyethylene compound (mass part)]×100
<Preparation of isocyanurate derivative>
Preparation example 1
1,3-Xylylene diisocyanate (m-XDI, Mitsui Chemicals, Inc.) was used in a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube and a cooling tube under a nitrogen atmosphere so as to have the formulation shown in Table 1. Manufactured), an antioxidant (2,6-di(tert-butyl)-4-methylphenol, BHT, a hindered phenol-based antioxidant), and a co-catalyst (tetraphenyl dipropylene glycol diphosphite, organic suboxide Phosphate ester, trade name: JPP-100, manufactured by Johoku Chemical Industry Co., Ltd. The isocyanate group concentration in this charging liquid was 44.7% by mass.

Next, after adding a 37 mass% solution of tetrabutylammonium hydroxide (TBAOH) as an isocyanurate-forming catalyst to this charging solution so that the solid content conversion would be the formulation shown in Table 1, it is shown in Table 1. Under the reaction conditions (reaction start temperature, ultimate temperature and reaction time), an isocyanurate-forming reaction was carried out.

Then, the obtained reaction liquid is passed through a thin film distillation apparatus (temperature 150° C., vacuum degree 50 Pa) to remove unreacted xylylene diisocyanate and the like, and to obtain an isocyanurate derivative (XDI nurate) of xylylene diisocyanate. Prepared. The distillation yield is shown in Table 1.

Table 1 shows the conversion rate of the isocyanate group in this reaction (that is, the conversion rate of isocyanurate), the amount of alcohol modification in the isocyanurate derivative, the isocyanate group concentration, and the trimolecular area ratio.

Preparation Examples 2-7
1,3-Xylylene diisocyanate (m-XDI, Mitsui Chemicals, Inc.) was used in a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube and a cooling tube under a nitrogen atmosphere so as to have the formulation shown in Table 1. Manufactured), the antioxidant shown in Table 1, and the co-catalyst shown in Table 1. Table 1 shows the isocyanate group concentration in the charging solution for the urethanization reaction.

Next, alcohols were added to this charging solution so as to have the formulation shown in Table 1, and the urethanization reaction was carried out under the reaction conditions (reaction temperature and reaction time) shown in Table 1. Table 1 shows the equivalent ratio (NCO/OH) of the isocyanate group of 1,3-xylylene diisocyanate to the hydroxyl group of 1,3-butanediol.

Then, the reaction solution was cooled to 60°C. Table 1 shows the isocyanate group concentration of the reaction solution after the urethanization reaction.

Then, to this reaction solution, a 37 mass% solution of tetrabutylammonium hydroxide (TBAOH) was added to the reaction solution as an isocyanurate-forming catalyst so that the primary addition amount shown in Table 1 in terms of solid content was obtained. An isocyanurate-forming reaction was performed. Then, the above methanol solution of TBAOH was added to the reaction solution so that the solid content conversion would be the secondary addition amount shown in Table 1, and after the reaction time shown in Table 1 from the start of the reaction, the isocyanurate-forming reaction was completed. Ended. Table 1 shows the reaction start temperature and the maximum temperature reached in the isocyanurate-forming reaction, and the isocyanate group concentration of the reaction liquid after the isocyanurate-forming reaction.

Then, the obtained reaction liquid is passed through a thin film distillation apparatus (temperature 150° C., vacuum degree 50 Pa) to remove unreacted xylylene diisocyanate and the like, and isocyanurate of xylylene diisocyanate modified with alcohols. A derivative (XDI nitrate) was prepared. The distillation yield is shown in Table 1.

Table 1 shows the conversion rate of the isocyanate groups (urethane conversion rate and isocyanurate conversion rate) in this reaction, the amount of alcohol modification in the isocyanurate derivative, the isocyanate group concentration and the trimolecular area ratio.

Details of the abbreviations in Table 1 are shown below.

m-XDI: 1,3-xylylene diisocyanate (manufactured by Mitsui Chemicals, Inc.),
1,3-BG: 1,3-butanediol, manufactured by Tokyo Chemical Industry Co., Ltd.
IBA: isobutyl alcohol, manufactured by Tokyo Chemical Industry Co., Ltd.,
JPP-100: Tetraphenyl dipropylene glycol diphosphite (aromatic organic phosphite ester, manufactured by Johoku Chemical Industry Co., Ltd.),
JP-310: Tridecyl phosphite (aliphatic organic phosphite ester, manufactured by Johoku Chemical Industry Co., Ltd., product name),
BHT: 2,6-di(tert-butyl)-4-methylphenol (also known as dibutylhydroxytoluene, BHT, hindered phenol antioxidant) hindered phenol antioxidant),
Irg1076: Irganox 1076 (hindered phenolic antioxidant, manufactured by Ciba Japan Co., Ltd., product name),
TBAOH: Tetrabutylammonium hydroxide.

<Preparation of other isocyanate derivatives>
Preparation Example 8
Takenate D-170N (isocyanurate derivative of hexamethylene diisocyanate (HDI), solid content 100% by mass, isocyanate group content 20.7%, manufactured by Mitsui Chemicals, Inc.) was prepared as an isocyanate derivative.

Preparation Example 9
Takenate D-110N (a trimethylolpropane (TMP) adduct of xylylene diisocyanate, an isocyanate group content of 11.5% by mass, a solid content of 75% by mass, a solvent: ethyl acetate, manufactured by Mitsui Chemicals, Inc.) is prepared as an isocyanate derivative. did.

<Preparation of blocked isocyanate>
Examples 1-10 and Comparative Examples 1-6
In a reactor having a capacity of 2 L equipped with a stirrer, a thermometer, a cooler and a nitrogen gas introduction tube, at room temperature (25° C.), the isocyanate derivative (isocyanurate derivative or other isocyanate derivative) of each preparation example shown in Table 2 was prepared. Mass parts and 110 parts by mass of propylene glycol monomethyl ether acetate (PMA, solvent) were charged, and the number average molecular weight of 1000 was adjusted so that the ethylene oxide group content (EO%) in the reaction product would be the value shown in Table 2. Of poly(oxyethylene) methyl ether (methoxy polyethylene glycol, MePEG1000, polyoxyethylene compound) was charged.

Next, this charging liquid was heated to 90° C., and the isocyanate derivative and poly(oxyethylene)methyl ether were subjected to urethanization reaction until there was no change in the amount of residual isocyanate.

As described above, a PMA solution of the hydrophilic isocyanate derivative (reaction product) was prepared.

Table 2 shows the ethylene oxide group content in the hydrophilic isocyanate derivative (reaction product), the solid content concentration of the hydrophilic isocyanate derivative PMA solution, and the isocyanate group concentration of the hydrophilic isocyanate derivative PMA solution.

Next, 441 parts by mass of PMA was added to 735 parts by mass of the PMA solution of polyisocyanate, and the mixture was stirred, and then the blocking agent shown in Table 2 was added in an amount equal to that of the isocyanate group contained in the hydrophilic isocyanate derivative.

Then, the isocyanate group and the blocking agent were reacted at 40° C. for 2 hours. Then, it was confirmed that the isocyanate group had disappeared by measuring the FT-IR spectrum.

As described above, a PMA solution of blocked isocyanate was prepared. The solid content concentration of the PMA solution of blocked isocyanate was 60% by mass.

Then, 550 parts by mass of water was dividedly charged into 500 parts by mass of a PMA solution of blocked isocyanate at room temperature (25° C.) in several batches, and then PMA was distilled off from the mixed solution under reduced pressure. An aqueous dispersion of the blocked isocyanate (polyisocyanate component) was prepared. The solid content concentration of this aqueous dispersion was 40 mass %.

The aqueous dispersion of the blocked isocyanate was allowed to stand at 25° C. for 24 hours, and then the aqueous dispersibility of the blocked isocyanate was visually evaluated according to the following criteria. The one in a uniform state in which solid content separation (sedimentation) did not occur was evaluated as ◯, and the one in which a separated product (sediment) was observed was evaluated as x. The results are shown in Table 2.

<Preparation of polyurethane coating composition>
A dispersion liquid (polyol component) in which an acrylic polyol (trade name: RE4788, manufactured by Mitsui Chemicals, Inc.) was dispersed in water was prepared.

Then, the aqueous dispersion of the blocked isocyanate (polyisocyanate component) of each of the examples and the comparative examples is added to the acrylic polyol dispersion (polyol component) so that the hydroxyl groups of the acrylic polyol and the latent isocyanate groups of the blocked isocyanate are in the same amount. In this way, a polyurethane coating composition was prepared by stirring for 30 minutes. The solid content concentration of the final polyurethane coating composition was 30% by mass.

<Evaluation>
1. Film Formability Test The polyurethane coating composition prepared as described above was applied onto a galvanized steel sheet with an applicator of 100 μm, dried at 23° C. for 3 hours, and then cured at 150° C. for 30 minutes. Then, the cured coating film was aged at 23° C. and 55% relative humidity for 7 days.

And the film-forming property of the coating film was evaluated according to the following criteria.

A uniform film with no cracks or streaks over the entire coating film was rated as ◯, and a film where the surface of the coating film was partially cracked or streaked was rated as Δ.

2. Cross-cut test A coating film was formed on a galvanized steel sheet in the same manner as the above film-forming property test. In addition, a coating film was formed on the tin plate in the same manner as in the above film-forming test except that the galvanized steel plate was changed to the tin plate.

Then, using a tin plate and a galvanized steel plate on which each coating film was formed, the adhesion of each coating film was determined according to JIS K5600-5-6 by the number of adhesion sites after peeling the tape according to the following criteria. evaluated.

When the number of pieces adhered without peeling was 25, it was evaluated as ◯ when it was more than 10 and less than 25, and when it was 10 or less. The results are shown in Table 2. In Table 2, the number of adhered pieces in 25 squares without peeling was read and described as "number of adhered pieces/25".

3. MEK rubbing test A coating film was formed on a tin plate in the same manner as in the above film-forming test except that the galvanized steel plate was changed to a tin plate. Then, each cured coating film was rubbed with gauze dipped in methyl ethyl ketone (MEK), and the number of times until peeling or scraping was visually observed was measured, and evaluated according to the following criteria.

A sample having a rubbing count of 200 or more was rated as O, a sample having a rubbing count of 100 to less than 200 was rated as B, and a rubbing count of less than 100 was rated as X. The results are shown in Table 2.

4. Weather resistance test A coating film was formed on a PMMA plate in the same manner as in the above film-forming test except that the galvanized steel plate was changed to a PMMA plate. Then, each cured coating film was subjected to an accelerated weather resistance tester (due panel light control weather meter, manufactured by Suga Test Instruments Co., Ltd.) in the daytime (60° C.×relative humidity 10%×4 hours×light irradiation), at night. Treatment was performed for 600 hours in a cycle of (50° C.×95% relative humidity×4 hours×no light irradiation). The coating film before and after the treatment was measured with a color difference meter (SE2000, manufactured by Nippon Denshoku Industries Co., Ltd.), and the color difference (ΔE) before and after the treatment was evaluated according to the following criteria.

A ΔE of less than 5.0 was evaluated as ◯, a ΔE of 5.0 or more and less than 10.0 was evaluated as Δ, and a ΔE of 10.0 or more was evaluated as x. The results are shown in Table 2.

5. Pencil hardness test A coating film was formed on a galvanized steel sheet in the same manner as the film forming test. Then, the pencil hardness of the coating film was measured based on JIS K5600-5-4 and evaluated according to the following criteria.

A pencil hardness of HB or more was evaluated as ◯, and a pencil hardness of B or less was evaluated as x. The results are shown in Table 2.

6. Wet thermal expansion coefficient The aqueous dispersion of the blocked isocyanate (polyisocyanate component) of each of the examples and comparative examples was added to the aqueous dispersion of the polyurethane polyol (polyol component, W-5661, solid content 35% by mass, manufactured by Mitsui Chemicals, Inc.). A polyurethane coating composition was prepared by adding polyurethane polyurethane/blocked isocyanate so that the solid content ratio was 5/3 and stirring for 30 minutes. The concentration of the polyurethane coating composition was adjusted by diluting it with water so that the final solid content concentration was 30% by mass.

Next, the polyurethane coating composition was applied onto a polypropylene plate with a 100 μm applicator, dried at 23° C. for 3 hours, and then cured at 150° C. for 30 minutes. Then, the cured coating film was aged at 23° C. and 55% relative humidity for 7 days.

Then, a test piece (20 mm×20 mm) was cut out from the polypropylene plate on which the coating film was formed, and the wet thermal expansion coefficient under the conditions of temperature 25° C., humidity 80%, and 3 hours using TMA-4000SE manufactured by NETZSCH. It was measured and evaluated according to the following criteria.

A coefficient of wet thermal expansion of less than 2.0% was evaluated as O, a coefficient of wet thermal expansion of 2.0% or more and less than 3.0 was evaluated as Δ, and a coefficient of wet thermal expansion of 3.0% or more was evaluated as x. The results are shown in Table 2.

Details of the abbreviations in Table 2 are shown below. It should be noted that those overlapping with Table 1 are omitted.

DMP: 3,5-dimethylpyrazole, manufactured by Tokyo Chemical Industry Co., Ltd.,
MEKO: methyl ethyl ketoxime, manufactured by Tokyo Chemical Industry Co., Ltd.,
MePEG1000: poly(oxyethylene) methyl ether, number average molecular weight 1000, manufactured by Toho Chemical Industry.

Claims (5)

A blocked isocyanate in which the isocyanate group of polyisocyanate is blocked by a blocking agent,
The polyisocyanate includes an isocyanurate derivative of xylylene diisocyanate and a reaction product of a polyoxyethylene compound,
Content of the ethylene oxide group in the said reaction product is 15 mass% or more and 30 mass% or less, Blocked isocyanate characterized by the above-mentioned. The blocked isocyanate according to claim 1, wherein the isocyanurate derivative of xylylene diisocyanate is modified with alcohols. The blocked isocyanate according to claim 2, wherein the modified amount of the alcohols in the isocyanurate derivative of xylylene diisocyanate is 0.1% by mass or more and 8.5% by mass or less. The blocked isocyanate according to claim 2, wherein the alcohol includes a divalent aliphatic alcohol. The blocked isocyanate according to any one of claims 1 to 4, wherein the blocking agent contains a pyrazole compound and/or an oxime compound.